Carbohydrate-based anti-infective agents can disrupt complex carbohydrate recognition events vital to the infective mechanisms of pathogens, representing an untapped wealth of therapeutics. The promise of carbohydrate-based anti-infective is that they are less prone to the evolution of microbial resistance, because, carbohydrate ligands themselves are invariant, and carbohydrate recognition is essential to pathogenic function. As such, carbohydrate-based anti-infective can better thwart the looming public health threats posed by the evolution of resistant microbial strains. The goals of the proposed research are to specifically develop new carbohydrate-based anti-infective agents that address the recent rise of resistant strains of pathogenic bacteria and influenza, as detailed in two aims targeting: 1) bacterial transglycosylase, and 2) the influenza coat proteins hemagglutinin and neuraminidase. Transglycosylase (TGase) is the enzyme responsible for assembling the carbohydrate backbone of the bacterial cell wall: it is essential, accessible, and less prone to evolving antibiotic resistance due to its recognition of the invariant oligosaccharide backbone of the peptidoglycan. Our efforts have primed TGase for long-awaited antibiotic development against dangerous gram-positive strains of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). In extension, the Mycobacterial TGase will be established for the development of anti-tuberculosis agents, which are in great need due to the alarming rise of multi- and extensively-drug resistant Mycobacterium tuberculosis (MDR-/XDR-TB). Routes for the specialized synthesis of carbohydrate-based substrate analogs, transition state inhibitors, and novel drug- like motifs are proposed for targeting gram-positive and Mycobacterial TGases. Hemagglutinin (HA) and neuraminidase (NA) are influenza coat glycoproteins that are susceptible to inhibition by sialic acid derivatives, which interfere with necessary recognition of sialosides (i.e. complex carbohydrates that end with a sialic acid). They are also targets of the adaptive immune response, which can generate neutralizing antibodies to antigenic protein epitopes, particularly with HA. Strategies for inhibition and immunization need to be improved, as high rates of viral mutation lead to resistance against antiinfluenza agents (e.g., the rapid emergence of Tamiflu resistant swine flu during the 2009 level-6 pandemic outbreak) and antigenic drift (i.e., escape from protective immunity). Looming pandemic threats further hasten this need. Antiinfluenza agents are designed herein with focus on establishing a higher barrier to resistance and understanding how resistant mutations affect NA-sialoside interactions. A strategy for a carbohydrate-modified HA protein vaccine is presented, with attention directed toward maximizing cross-reactive immunity.